Fastener setting tools

ABSTRACT

An explosively-actuated fastener setting tool comprises a barrel which can be moved forwardly after firing in order to open a breach for loading of a fresh charge. Forwards movement of the barrel also enables a spring-loaded stop to pivot through a slot in the barrel and engage the head of a firing piston to thereby reset the piston in the barrel. In the normal, breach-closed position of the barrel, the stop is fully retracted from the barrel. The configuration permits increased opening movement of the barrel. Further stops between the barrel and tool body engage in a forward position of the barrel to prevent the rear end of the barrel slot from impacting against the pivotal stop.

The present invention relates to explosively actuated tools for settingfasteners such as nails or pins into a substrate composed of arelatively hard material such as concrete, masonry, or steel.

FIGS. 1 to 4 show an explosively actuated setting tool of the typedisclosed in U.S. Pat. No. 3,066,302. In these figures, FIGS. 1 and 2show respectively, a receiver assembly and a barrel assembly, and FIG. 3shows the barrel assembly mounted in the receiver assembly, with thetool ready to fire. FIG. 4 shows the barrel assembly pulled into aforward position to open a breach of the tool for re-setting a firingpiston and for loading a fresh charge.

The barrel assembly comprises a barrel 2 containing a firing piston 4. Acharge chamber 6 at the rear of the barrel 2 receives an explosivecharge 8 which is fired by a firing pin 10 in the receiver assembly(FIG. 1) to propel the piston 4 forwardly to drive a fastener 12positioned in the forward end of the barrel into a substrate. A slot 14formed in the underside of the barrel 2 is adapted to receive aspring-loaded stop pawl 16 for re-setting the piston 4 after firing, thepawl 16 being carried at the front end of the receiver assembly. At theforward end of the slot 14, a cam surface 18 acts to displace the pawl16 out of the path of the piston 4 when the barrel 2 is in its rearward,ready-to-fire position as shown in FIG. 3. When the tool has been fired,the piston 4 normally stops with its head 4a positioned just behind thepawl 16, this stop position being obtained when the forward end of thepiston 4 is at the forward end of the barrel 2, with the fastener havingbeen driven fully home into the substrate so that its head flush withthe surface of the substrate. The cam 18 displaces the pawl 16 out ofthe possible path of the piston head 4a in case the piston 4 over-drivesthe fastener into the substrate should the substrate be unusually soft.

In order to reset the tool after firing, the barrel assembly is movedforwardly into the position shown in FIG. 4. At the start of thismovement, the cam 18 moves with the barrel 2 forwardly away from thepawl 16 thus allowing the pawl 16 to move upwardly through the slot 14to engage the front face of the piston head 4a and prevent the piston 4moving forwardly with the barrel 2. When the barrel is in its forwardposition (FIG. 4), the piston head 4a is at the back end of the barrel 2and has thus been reset relative to the barrel 2 in preparation for thenext firing. In the forward position of the barrel 2 the breach 20 isopened behind the barrel 2 to permit extraction of the previous charge 8and loading of the fresh charge.

In this previously proposed tool, the pawl 16 always lies within theslot 14 in the barrel 2, but in the rearmost position of the barrel 2(the ready-to-fire configuration of the tool), the pawl 16 is held bythe cam 18 out of the possible path of the piston head 4a. The length ofthe slot 14, and thus the degree of opening of the barrel is determinedby the maximum length of fastener which can be driven by the tool. Toolsdesigned for relatively short fasteners accordingly have only a limiteddegree of opening, and hence only a restricted access which may causedifficulties in removal of the fired charge and loading of the freshchange. These difficulties become apparent for operatives who wearprotective gloves and/or work in cold conditions.

According to the present invention, there is provided anexplosively-actuated tool for setting a fastener into a substrate,comprising a body, a barrel containing a firing piston operative upondetonation of an explosive charge to drive a fastener in the forward endof the barrel, said barrel being movable in the body from a rearposition in which the tool is ready to fire to a forward position inwhich a breach is opened for loading of a fresh charge and stop meanscarried by the body and extendable into the barrel to engage the pistonduring the forward movement of the barrel to reset the piston rearwardlyrelative to the barrel in preparation for the next firing, said stopmeans being mounted for movement out of the barrel upon subsequentrearwards movement of the barrel to close the breach.

Preferably, the stop means is pivotal between its operative andretracted positions.

An embodiment of the invention will now be described, by way of exampleonly, with reference to the accompanying drawings, in which:

FIG. 5 shows a tool in accordance with our embodiment of the inventionin its ready-to-fire configuration;

FIG. 6 shows the tool of FIG. 5 with the barrel in its fully openposition;

FIG. 7 is a perspective view of a retractor pawl;

FIG. 8 shows the firing mechanism of the tool; and

FIG. 9 is a section on line Y of FIG. 8.

The tool of the preferred embodiment of the invention differs from thatof FIGS. 1 to 4 primarily in the configuration and operation of the stoppawl. More particularly, the slot 14 opens downwardly into a larger slot15 and a stop pawl 30 carried at the front end of the receiver assemblyis pivotally mounted. The pawl 30 comprises a guide portion 32 adaptedto ride along the underside of the slot 14 in the barrel 2 and a stopportion 34 which projects through the slot 14 into the path of thepiston head 4a. An inclined ramp surface 36 is formed at the forwardside of the stop portion 34. A torsion spring 38 acts on the pawl 30 topivotally bias the pawl 30 into its operative position in which its stopportion 34 projects through the slot 14.

In the ready-to-fire position of the tool (FIG. 5) the forward end ofthe slot 14 is positioned a substantial distance behind the pawl 30which has pivoted into a retracted position fully removed from thebarrel 2, to lie beneath the forward end of the barrel 2. The retractionof the pawl 30 completely from the barrel 2 means that the stroke of thebarrel between its rear position and its forward open position is nolonger limited by the length of the slot 14 and thus the maximum lengthof the fastener being fired and, therefore, the stroke of the barrel canbe extended to permit sufficient, and increased, access to the openedbreach 20 behind the barrel 2 even with tools designed for use withshort fasteners.

The increased opening movement also permits driving of an automaticloading mechanism (if required) for the charges and/or the fasteners dueto the increased mechanical advantage derived from the increased strokelength of the barrel.

The construction will now be described in greater detail.

In the ready to fire position of FIG. 5, the firing mechanism, whichwill be described subsequently, has been cocked upon rearward pressurehaving been applied to the front of the barrel 2 consequent on theoperator forcing the barrel against the substrate.

In this position, the pawl 30 has swung out of its operative position,against the bias of the torsion spring 38 so that a face 46 of the pawl30 lies against the underside of the forward end of the barrel. Also inthis position, a shoulder 40 at the end of the slots 14 and 15 is justclear of a stop 42 on the receiver assembly so that the stop 42 is notsubject to the recoil forces at firing, these forces being taken throughbreech faces 49. In this position, the stop 42 controls the radialalignment, as well as the forward movement, of the barrel 2, by engagingthe sides of the slot 15.

Although in the embodiment shown, the stop acts in conjunction with theslot 15 through which the pawl 30 projects into the slot 14, a separateslot, angularly displaced from the slot 14 may be provided forcontrolling the barrel alignment and movement in conjunction with anappropriate stop on the receiver assembly.

After firing, the barrel 2 is moved forwardly by the operator. As theforward end of the slots 14 and 15 passes over the pawl 30, the pawlpivots upwardly under its spring bias so that the stop portion 34 entersthe slots 14 and 15 with the guide portion 32 resting against theunderside of the slot 14. The stop portion 34 thereby lies in front ofthe path of the piston head 4a to stop the piston and therefore resetthe piston 4 relative to the barrel 2 upon further forward movement ofthe barrel. The forward stop position of the barrel 2 is defined byengagemet of a shoulder 15a at the rear end of the slot 15 with the rearface of the stop 42 on the receiver assembly. In this position a smallclearance is left between a shoulder 14a at the rear end of the slot 14and the rear face of the pawl 30, thus ensuring that the relativelyfragil pawl 30 is required to restrain only the piston 4 and is notsubjected to high impact loads generated when the barrel is vigorouslypulled or 'thrown' forward.

The barrel 2 may then be moved to its closed position, the piston 4having been reset in the barrel 2 and a fresh charge and fastener havingbeen loaded. Towards the end of the closing movement, the forward end ofthe slots 14 and 15 engages the inclined ramp surface 36 of the pawl 30and pivots the pawl 30 downwardly to permit the forward end of thebarrel 2 to move past the pawl 30.

With reference to FIGS. 8 and 9, the firing mechanism of the receiverassembly comprises a block 50 mounted for sliding movement in thereceiver assembly and which carries the major components of themechanism. The block 50 is biased forwardly by means of a compressionspring 52. The block 50 carries a firing pin 54 loaded by means of acompression spring 55, the pin 54 being held in a cocked position bymeans of a spring-biased gate 56, which engages a shoulder 54a on thepin 54. When the gate 56 is displaced by operation of the trigger 58 thefiring pin 54 is propelled forwardly under its spring bias so that itstip 54b projects through an aperture 60 at the front of the block 50into engagement with the case of the charge 8 carried at the rear of thebarrel 2 in the ready-to-fire position. After firing, the firing pin 54is reset by the forward movement of the barrel 2 as will now bedescribed.

When the barrel is moved forwardly to reset the piston 4 and permitloading of a fresh charge as previously described, the block 50 togetherwith the firing pin 54 is moved forwardly by the compression springs 52and 55 to a forward stop position defined by engagement of a rear stopsurface 62 of the block 50 with a transverse stop pin 64 which extendsthrough the block 50 to be anchored at each end in the body of thereceiver assembly as shown in FIG. 9. The head 54c of the firing pin 54also engages the stop pin 64 in the forward stop positioon. In thisposition, the shoulder 54a of the firing pin 54 is rearwardly of thegate 56 and the gate has moved under its spring bias into contact withthe reduced-diameter front end portion of the firing pin 54. Uponsubsequent rearwards movement of the barrel 2, the rear face of thebarrel 2 engages the front face of the block 50 and pushes the blockbackwards. The block 50 will move relative to the firing pin 54 untilthe gate 56 contacts the shoulder 54a of the firing pin and continuedrearwards movement of the block 50 will carry the firing pin 54backwards against the bias of the spring 55 to re-cock the pin.

In the mechanism described, the single stop pin 64 acts as a forwardstop for both the block 50 and the firing pin 54 and leads to asignificantly simplified construction in comparison with previouslyproposed mechanisms which incorporate separate stops.

The embodiment has been described by way of example only andmodifications are possible within the scope of the invention.

I claim:
 1. An explosively-actuated tool for setting a fastener into asubstrate, comprising a body, a barrel containing a firing pistonoperative upon detonation of an explosive charge to drive a fastener inthe forward end of the barrel, said barrel being movable in the bodyfrom a rear position in which the tool is ready to fire to a forwardposition in which a breach is opened for loading of a fresh charge, saidbarrel including a longitudinal slot closed at its forward and rear endsand opening into the interior of the barrel, stop means movable betweenan operative position in which the stop means extends through the slotin the barrel into the inteior of the barrel to engage the piston duringthe forward movement of the barrel to reset the piston rearwardlyrelative to the barrel in preparation for the next firing, and aretracted position withdrawn from the slot in the barrel upon subsequentrearwards movement of the barrel to close the breach, the retracted stopmeans being located forwardly of the forward end of the slot when thebarrel is in its rear position, means for urging said stop means to itsretracted position upon movement of said barrel into its rear position,means for moving said stop means to its operational position uponmovement of said barrel toward its forward position, a shoulder on saidbarrel, and a forward stop on the body, said forward stop on the bodybeing engageable with said shoulder on the barrel in the forwardposition of the barrel to define a forward stopped position for thebarrel, said stop means being spaced forwardly from the rear end of theslot when the barrel is in its forward stopped position for preventingengagement of said stop means with said rear end of said slot upon theinterengagement of the said shoulder on said barrel and said forwardstop on said body if said barrel is thrust forward.
 2. The toolaccording to claim 1, wherein the movement of said stop means includespivotal movement about a pivot axis.
 3. The tool according to claim 1,wherein the interengagement of the said shoulder on said barrel and siadforward stop on said body prevents the rear end of the slot fromimpacting against the stop means when said barrel is thrust forward. 4.The tool according to claim 1, wherein the means for urging said stopmeans is a spring.
 5. The tool according to claim 1, wherein the meansfor urging said stop means is resiliently biased towards its operativeposition and said stop means further comprises a guide portion adaptedto engage the external surface of the barrel in the operative position,a stop portion projecting from the guide portion and extending throughthe slot in the operative position, and a ramp extending through theslot in the operative positoiin, and a ramp portion engageable with theforward end of the slot during movement of the barrel to cause pivotalmovement of the stop means to its retracted position as the forward endof the slot passes the stop means during rearwards movement of thebarrel to close the breach.
 6. The tool according to claim 5, whereinthe guide portion comprises a guide surface adapted to engage theexternal surface of the barrel at each side of the longitudinal slot inthe barrel when the stop means is in its operative position, said guidesurface having opposed longitudinal sides, and wherein the stop portionextends from a part of the guide portion intermediate the longitudinalsides.
 7. A tool according to claim 5, wherein the guide portion and thestop portion are on the same side of the pivot axis of the stop means.8. A tool according to claim 6, wherein the guide portion and the stopportion are on the same side of the pivot axis of the stop means.